The invention relates to an instrument with a proximal headpiece, with a shaft that can be deflected at least in the distal end area via a deflection mechanism, with a control element via which deflection movements of the shaft can be controlled by movement of control wires of the deflection mechanism, and with a lock for locking the deflection mechanism.
Such an instrument is known from DE 37 29 131 C1.
Such instruments are now in widespread use.
One field of use are medical instruments. Endoscopic instruments used for this purpose have a shaft portion that can be angled, at least at the distal end area.
It is in this way possible to introduce the shaft initially in an elongate state into a cavity of a living body. This can be done, for example, via a trocar or trocar sleeve inserted into a body or by way of natural orifices of the body, for example the mouth, the anus or urethra. The shaft can be deflected laterally within the cavity, such that, for example in the case of endoscopes, views can be gained to either side of the rectilinear direction. The shafts themselves can be of a rigid or flexible design, the crucial point being that the distal end area can be deflected. In the case of instruments serving purely as endoscopes, this provides an all-round view within the body cavity. If operating instruments, for example a needle holder, are mounted at the distal end, it is also possible to perform manipulations, e.g. suturing procedures, at locations within the cavity that cannot be reached by a rectilinear instrument.
A further field of use lies in particular in endoscopes used to inspect technical equipment.
One field of use is the inspection of structural parts that are difficult to access, e.g. the rear ends of the air vanes of aircraft turbines. By using deflectable endoscopes, such locations that are difficult to access can be inspected without dismantling the turbines.
Other fields of use are, for example, engine construction or bodywork construction, the latter case in particular requiring the inspection of cavity seals within hollow bodywork structures of complicated form.
Further technical fields of use are inspections of buildings or masonry.
The range of use of such instruments with deflectable shafts is becoming ever wider.
To permit the deflecting movement, a deflection mechanism is provided which is in most cases composed of control wires that are routed along the shaft and are connected to a control element at the headpiece.
For example, if the distal end is to be deflected in one plane away from the rectilinear orientation, two diametrically opposite control wires are provided. To permit deflection, one of the two control wires is now pulled in and the diametrically opposite control wire is pushed out, as a result of which the flexible end area of the shaft is curved or bent outwards in one plane. Such a control element can, for example, have a reel or roller on which the two control wires are secured. Rotation of the reel by the control element causes one control wire to be unwound in one direction, while at the same time the other control wire is reeled in. In the opposite direction of rotation, exactly the reverse procedure takes place.
It is thus possible for the deflectable area of the shaft to be deflected through almost 180° to both sides of the longitudinal axis.
In further developments, the deflection mechanism has two such pairs of control wires, which are arranged offset from each other by 90°, such that the deflectable area of the shaft can be deflected in two planes orthogonal to each other. It has become established practice to provide two control elements that operate independently of each other, as is known from DE 199 24 440 A1, for example. A combination of both movements permits the positioning of the distal end on a sphere surface.
It has now been observed in practical application that, after the deflection, a relatively strong restoring moment acts on the shaft, and this tends to bring the deflected shaft back to a more or less rectilinear state. In a bent flexible shaft, the outer envelope is compressed on one side and stretched like a rubber sheet on the other side. This results in relatively strong restoring forces. If the control wires are made of relatively stiff wire, restoring forces also occur upon deflection, that is to say bending, of the wires.
To avoid unwanted restoring of the deflected bent shaft, locks were developed that lock the deflected shaft against return from a defined position of deflection.
In addition to the deflection mechanism, it was thus also necessary to provide a locking mechanism via which the shaft can be locked against return from a respective position of deflection.
In DE 37 29 131 C1 mentioned at the outset, this is achieved by a combined brake lever and control lever. The lever, whose central rotation axle is connected to a reel on which the control wires can be wound and unwound, constitutes the control element of the deflection mechanism. If the shaft has been deflected into a defined position by means of the control lever, the lever has to be turned in another direction in order thereby to actuate a brake mechanism, which is designed to prevent restoring of the deflected area, i.e. is designed to block this movement. However, a certain amount of movement back and forwards for fine correction is still possible as before.
If the shaft is to be moved to another position of deflection or is to be made rectilinear again, the combined brake lever and control lever has to be moved in one direction to initially release the brake mechanism and then has to be moved in another direction in order to move the control wires of the deflection mechanism.
This is disadvantageous in the sense that different directions of movements and different manipulations have to be performed using one and the same control element, in order to be able to carry out the different procedures, namely, on the one hand, actuation of the deflection mechanism and, on the other hand, actuation of the brake mechanism.
In a starting position, the brake mechanism is free, and the deflection mechanism can now be actuated by the lever. The lever then has to be moved deliberately in another direction in order to activate the brake mechanism.
This is ergonomically unfavourable, requires a high level of attention and poses the danger of the deflected shaft moving out of position if the brake mechanism is not correctly actuated.
Moreover, the operator does not immediately know whether the lever is in a position in which it can be turned in order to actuate the deflection mechanism, or whether it is already in the brake function, since for this purpose it only has to be lifted a few millimeters from the rotation position.
This poses the problem that if pressure is inadvertently applied to the lever, the brake function is released and the deflected shaft moves.
This is fatal in the medical field in particular, for example if a surgical intervention is being performed with the deflected end.
It is, therefore, an object of the present invention to develop an instrument of the kind mentioned at the outset such that the control and in particular the locking and unlocking can be carried out safely, particularly using one hand.